A multidisciplinary study of the major psychoses was initiated in Nov. 1977. Approximately 100 psychotic patients are evaluated each year with the Present State Examination, a detailed psychiatric history and family history schedule, and longitudinal assessment of clinical change using instruments such as the Schedule for Affective Disorders Change scale. The patients are also studied with a variety of biochemical, neuroendocrine and neurophysiological measures. At intervals of at least one year, follow-up interviews will be collected. Specific research projects include: 1) comparison of various criteria for the diagnosis of schizophrenia; 2)stability of acute symptoms upon readmission; 3) comparison of symptoms, history, response to lithium of patients with schizoaffective illness, affective illness and schizophrenia; 4) H-reflex recovery curve as a function of psychiatric diagnosis; 5) prolactin and growth hormone response to apomorphine; 6) neuroleptic blood levels as a predictor of clinical response and correlate of serum prolactin levels; 7) platelet and plasma monoamine oxidase activity in schizophrenia; 8) dose-response curves for effects of neuroleptics on serum prolactin levels and H-reflex in schizophrenics and controls; 9) serum DBH activity in psychotic depression; 10) effect of tricyclic anti-depressants on rat plasma prolactin levels following low dose or high dose 5-hydroxytryptamine; 11) supersensitivity to serotonin agonist induced by multiple injections of serotonin agonists; 12) ability of dopamine agonists to decrease rat plasma prolactin levels; 13) effect of alpha-methylparatyrosine and monoamine oxidase inhibitors on serum prolactin levels in man; 14) studies of 3H-spiroperidol and 3H-dihydroergocryptine binding in rat pituitary and striatum; 15) effect of amantadine on serum prolactin in man and laboratory rats.